Hi. I am recently designing biomedical antennas.
The problem is the permittivity difference between the skin and the air is too big, so I am having difficulties in delivering RF power to the inside of the body.
As far as I know, in the case of ultrasound imaging, some gel-type materials are used to match the acoustic impedance between the tissue and the air.
Is there anyone who knows any materials that can be used in my design?
I think it should be not solid. Something with some elasticity will be good.
You need progressive adaption between the two media. Think of successive layers of materials with increasing permittivity. The concept is similar to impedance adaption using tapered transmission lines.
If you also need to focus the energy at some specific point on the skin, then we are talking about a multilayer dielectric lens.
Check something along these lines here:
https://ieeexplore.ieee.org/document/5293950?arnumber=5293950
https://ieeexplore.ieee.org/document/9232223
Hmm my intention is to send the EM signal to the heart. But thanks for your comment. Yes, that is a good comment. I will check the paper you posted.
OK, then check the second reference, we present an idea on how to achieve this using two lenses.
Dear Min-Gyo,
this problem is similar to the well known acoustic matching problem for any kind of ultrasound application e.g. on the human body; however I do NOT see a strong motivation to any sort of GEL there..depending on the frequency and the type of tissue the effective epsilon would be probably somewhere between say 5 (fat like layer) and maybe around 40 (flesh , muscles) Thus it may be much easier to use a layer of alumina (eps around 10) as index mating material in front and as part of your antenna.Also watefilled small bags were applied for this purpose.
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